Sole construction with stretch flex zone

ABSTRACT

In accordance with one implementation, a sole construction includes a flexible membrane in a forefoot region of the sole construction. The flexible membrane interconnects a first rigid plate to a second rigid plate along a longitudinal axis of the sole construction. The flexible membrane is adapted to flex in the forefoot region responsive to a contact force, causing the first rigid plate to move relative to the second rigid plate.

BACKGROUND

During a typical running gait of a runner not wearing footwear, a foot lands first on a lateral side of the foot on a region of the foot underlying the fifth metatarsal bone. The runner's weight then settles on the middle and medial side of the foot, putting weight on one metatarsal at a time. As the foot lands, the joints and bones of the foot extend laterally, and the toes dorsiflex upward, toward the runner's body.

Some traditional shoes do not allow for this natural motion of the foot. For example, traditional track shoes are generally formed of a uniform, stiff sole. Rather than allow the metatarsals to land on the ground individually, these shoes can instead restrict and constrain the foot's motion. As a result, a runner's toes may move largely as a single unit, rather than as individual bones and joints. Restricting the movement of the bones and joints of the foot reduces efficiency and may be a factor contributing to injury.

SUMMARY

Implementations described herein may be utilized to address at least one of the foregoing problems by providing a shoe sole construction including a stretch flex zone in a forefoot region that makes it easier for the toes to bend away from the rest of the foot (i.e., to dorsiflex). In some implementations, the forefoot stretch flex zone is shaped to provide for independent movement of the metatarsal bones, joints, and toes of a user's foot.

This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. These and various other features and advantages will be apparent from a reading of the following Detailed Description.

BRIEF DESCRIPTIONS OF THE DRAWINGS

A further understanding of the nature and advantages of the present technology may be realized by reference to the figures, which are described in the remaining portion of the specification.

FIG. 1 illustrates a bottom plan view of an example sole construction with a stretch flex zone.

FIG. 2 illustrates a bottom plan view of an example sole construction including a stretch flex zone that interlinks a rigid forefoot plate and a rigid toe plate.

FIG. 3 illustrates a bottom plan view of another example sole construction including a stretch flex zone that interlinks a rigid forefoot plate and a rigid toe plate.

FIG. 4A illustrates an exploded elevation view of a sole construction with a stretch flex zone.

FIG. 4B illustrates an exploded plan view of a sole construction with a stretch flex zone.

FIG. 5 illustrates another elevation view construction during a mid-stance stage of the gait cycle.

FIG. 6 illustrates another elevation view of a sole construction during a toe-off stage of the gait cycle.

FIG. 7 illustrates example operations for energy conservation in a sole construction.

DETAILED DESCRIPTIONS OF THE DRAWINGS

Recent studies have shown that a “natural running” form can help to reduce the frequency and severity of some common running injuries. “Natural running” refers to a form of running that a runner adopts to reduce loading rates and protect the foot from excessive impact while moving quickly and efficiently. A runner practicing natural running form strikes the ground close to a point under the body's center of gravity with a relaxed foot rather than over striding (e.g., landing with the foot in front of the runner's center of gravity) with an aggressively dorsiflexed ankle.

In an efficient gait cycle, the runner lands lightly with a relaxed foot and avoids exaggerated joint positions and excessive use of muscular force. When pushing off from the ground during a “toe-off” phase of the gait cycle, the toes dorsiflex upward away from the metatarsals of the foot. This dorsiflexion of the toes applies a flexing force to the runner's shoe sole in a region underlying the forefoot, where the toes meet the metatarsals. When a hard material, such as a plastic or carbon plate, is included in this “flex zone” the runner expends energy bending the hard material. Much of the energy expended in bending the hard material is not returned to the runner and is instead lost to damping forces of the shoe sole, heat dissipation, etc. By decreasing the amount of energy utilized in bending material of a forefoot region, the amount of energy retained by the runner is increased, allowing a proportional increase in the runner's efficiency and speed.

Implementations disclosed herein provide a sole construction including a stretch flex zone in a forefoot region underlying the metatarsophalangeal joints of the foot. The stretch flex zone is formed by a stretchable membrane that interconnects a first rigid plate, substantially underlying the toes, to a second rigid plate, substantially underlying the metatarsals. The disclosed technology may be of particular benefit in shoes designed for speed, such as sprinting shoes including track spikes. However, the technology is also contemplated for use in a variety of other types of footwear including athletic shoes of many types (e.g., cross-training, walking, running, etc.), as well as shoes designed for biking, hiking, driving, and any garment where increased flexibility is desired between two or more rigid areas.

FIG. 1 illustrates a bottom plan view of an example shoe sole construction 100 with a stretch flex zone 120. The sole construction 100 includes a hindfoot or heel region 106, a midfoot region 104, a forefoot region 102, and a toe region 112. The heel region 106 underlies or substantially underlies the length and width of a heel of a runner's foot. The midfoot region 104 is positioned forward or anterior to the heel region 106, and underlies or substantially underlies the arch or “middle” region of the foot, which typically includes the region underlying the navicular, cuboid, and cuneiform bones of the foot. The forefoot region 102 is positioned forward or anterior to the midfoot region 104, and underlies or substantially underlies the ball of the foot. In particular, the forefoot region 102 underlies the metatarsal bones and metatarsophalangeal joints. The toe region 112 is anterior to the forefoot region 102, and underlies or substantially underlies the phalanges (i.e., toes). The terms “heel region,” “midfoot region,” “forefoot region,” and “toe region” are used throughout the application, as defined above.

The sole construction 100 includes a forefoot plate 108 in the forefoot region 102 and a toe plate 110 in the toe region 112. The forefoot plate 108 and the toe plate 110 are substantially rigid, planar components separated from one another and interconnected by a substantially flexible, stretchable material. As used herein, “substantially rigid” refers to a hardness in a range between about shore 40 D and shore 90 D. In one implementation, “substantially rigid” refers to a hardness of about shore 70 D. In contrast, the term “substantially flexible” refers to a hardness in a range between about shore 20 D and shore 60 D. In one implementation, “substantially flexible” refers to narrower range between shore 30 D and shore 45 D. Within any single implementation, a “substantially rigid” material has a hardness that is greater than a “substantially flexible” material.

The stretch flex zone 120 includes the flexible, stretchable material in the region between the forefoot plate 108 and the toe plate 110. The stretch flex zone 120 extends through the forefoot region 102 between lateral (outside) and medial (inside) sides of the sole construction 100, permitting the toe plate 110 to move relative to the forefoot plate 108. When the sole construction 100 is implemented in a shoe, the stretch flex zone 120 provides a zone of increased flexibility in a region substantially underlying a runner's metatarsophalangeal joints.

In FIG. 1, the forefoot plate 108 and the toe plate 110 are affixed to a ground-facing surface of the sole construction 100, providing a rigid, outer surface for contacting the ground and/or for affixing one or more “track spikes” or other friction-providing elements. In the implementation shown, track spikes (not shown) can be attached to each of a number of receiving divots (e.g., a receiving divot 116) on the toe plate 110 and the forefoot plate 108. In at least one implementation, a user can selectively attach and remove track spikes to the receiving divots 116. Other implementations may not include receiving divots or features for track spike attachment. For example, the forefoot plate 108, toe plate 110, and stretch flex zone 120 may be included in a walking or general-purpose athletic shoe that is not specially designed for speed or increased traction provided by track spikes.

The forefoot plate 108 and the toe plate 110 may form a portion of a ground-facing outer surface of the sole construction 100, as shown. However, in other implementations, the forefoot plate 108 and/or the toe plate 110 do not form part of the ground-facing outer surface. For example, the forefoot plate 108 and/or toe plate 110 may be coated with a protective or friction-providing material, such as a soft or hard rubber. Alternatively, the forefoot plate 108 and/or toe plate 110 may be embedded within the sole construction 100.

FIG. 2 illustrates a bottom plan view of an example sole construction 200 including a stretch flex zone 220. The stretch flex zone 220 includes a flexible, stretchable material (i.e., a flex-stretch material) that interlinks a rigid forefoot plate 208 and a rigid toe plate 210. Elongated slots (e.g., an elongated slot 214) in the rigid forefoot plate 208 and the rigid toe plate 210 separate each of the plates into different, articulated regions (e.g., an articulated region 218). In various implementations, the number, length, and positioning of such slots may vary. The slots are filled with the flex-stretch material and form a portion of the stretch flex zone 220. The articulated regions of FIG. 2 may each move independently of one another responsive to movement of an overlying metatarsal of a user's foot. Movement of each of the articulated regions may be in multiple cardinal directions. For example, the articulated region 218 may be able to twist about a torsional axis (e.g., an example torsional axis “Y”) and simultaneously about a lateral axis (e.g., a lateral axis X). Movement about such lateral axis may be bidirectional. For example, if a user lands with a forefoot plate first with the toe plate vertically higher due to dorsiflexion, the sole may rotate about the lateral axis toward the ground, as well as away from the ground during a toe-off phase.

Although other implementations are contemplated, the sole construction 200 includes four elongated slots (e.g., an example slot 214) extending into the forefoot plate 208. Each slot in the rigid forefoot plate 208 is substantially aligned with a corresponding slot formed in the rigid toe plate 210. Each of the articulated regions in the rigid forefoot plate 208 substantially underlies and provides support for one of the five metatarsals of the foot, while each of the articulated regions in the rigid toe plate 210 underlies and provide support for one of the toes of the foot. In another implementation, the articulated regions are formed in one rather than both of the rigid toe plate 210 and the rigid forefoot plate 208.

The articulated regions of the rigid forefoot plate 208 and the rigid toe plate 210 allow for independent movement of different metatarsals of the foot. For example, a runner may strike the ground on the lateral (i.e., outside) region of the foot, putting weight on the fifth (outermost) metatarsal. The metatarsals then contact the ground one at a time, from the outside in. As the remaining metatarsals contact the ground, the runner's weight settles onto the middle and then onto the medial (i.e., inner) side of the foot. A shoe including the technology illustrated in FIG. 2 may allow the metatarsals and/or toes of the user's foot to each “move” an associated articulated region in the forefoot plate 208 and/or toe plate 210 as the weight settles over that region. This allows for more natural movement of the foot, increasing running efficiency and reducing injury.

FIG. 3 illustrates a bottom plan view of another example sole construction 300 including a stretch flex zone 320. The stretch flex zone 320 includes a flexible, stretchable (i.e., “flex-stretch”) material that interlinks a rigid forefoot plate 308 and a rigid toe plate 310. Elongated slots (e.g., an elongated slot 314) in the rigid forefoot plate 308 and the rigid toe plate 310 separate each of the plates into different, articulated regions (e.g., an articulated region 318). The slots are vertically aligned with the flex-stretch material and form a portion of the stretch flex zone 320. The articulated regions of FIG. 3 may each move independently of one another responsive to movement of an overlying metatarsal of a user's foot.

In FIG. 3, the forefoot plate 308 and the toe plate 310 are affixed to a ground-facing surface of the sole construction 300, providing a rigid, outer surface for contacting the ground and/or for affixing one or more “track spikes” or other friction-providing elements. In the implementation shown, track spikes (not shown) can be attached to each of a number of receiving divots (e.g., a receiving divot 316) on the toe plate 310 and the forefoot plate 308. In addition, a number of friction providing elements (e.g., a friction providing element 330, 331) are formed on each of the forefoot plate 308 and the toe plate 310 to provide increased friction with between the sole construction 300 and the ground.

FIG. 4A illustrates an exploded elevation view of an example sole construction 400 with a forefoot stretch flex zone 420. FIG. 4B illustrates an exploded plan view of the sole construction 400 of FIG. 4A. Dashed lines indicate corresponding components of FIG. 4A and FIG. 4B.

The example sole construction 400 includes an upper 430, a midsole layer 418, a flex-stretch layer 422, a rigid toe plate 410, and a rigid forefoot plate 408. The upper 430 (shown in FIG. 4A) includes fabric forming a top of a shoe construction. Other implementations may not include either the upper 430 and/or the midsole layer 418. The upper 430 attaches to the midsole layer 418, which is sized and shaped to receive and substantially underlie and provide support for a user's foot. One or more cut-outs or depressions (not shown) may be formed in a ground-facing surface of the midsole layer 418 to receive one or more of the flex-stretch layer 422, the rigid toe plate 410, or the rigid forefoot plate 408. The midsole layer 418 can be formed of a variety of materials such as ethylene-vinyl acetate (e.g., EVA foam), or other foam or soft, pliable material. In one implementation, the midsole layer 418 is substantially more pliable (e.g., softer) than the flex-stretch layer 422.

The ground-facing surface of the midsole layer 418 is bonded to the flex-stretch layer 422. The flex-stretch layer 422 is positioned in a forefoot region of the sole construction 400, so as to underlie a user's metatarsals and metatarsophalangeal joints. A portion of the flex-stretch layer 422 extends into a toe region of the sole construction so that it is vertically aligned with the rigid toe plate 410. As used herein, “vertical alignment” refers to alignment about an axis (e.g., the z-axis) that is substantially perpendicular to both a lateral (e.g., the x-axis) and torsional axis (e.g., the y-axis) of the sole construction 400. Another portion of the flex-stretch layer 422 extends toward a midfoot region of the sole construction 400 so that it is vertically aligned with the rigid forefoot plate 408.

The flex-stretch layer 422 is substantially planar and may have either a fixed or variable thickness. In one example implementation, the flex-stretch layer 422 has a fixed thickness of between about 1-2 mm. In the same or another implementation, the flex-stretch layer 422 is a variable thickness layer with a region of an increased thickness forming a perimeter (e.g., an “outline”) around the stretch flex zone 420. For example, a boundary separating the stretch flex zone 420 from either the rigid forefoot plate 408 or the rigid toe plate 410 may be raised by an additional 1 mm from the remainder (e.g., interior) of the flex-stretch layer 422. This design allows the stretch-flex layer 420 to be fitted precisely to the rigid forefoot plate 408 and/or the rigid toe plate 410, and may also allow for greater independent plate articulation.

A variety of materials are suitable for use in the flex-stretch layer 422 including without limitation elastic, DuPont™ Hytrel®, natural or synthetic gum rubber, and various thermoplastic elastomers such as polyether block amides (e.g., Pebax®). The hardness of the flex-stretch layer 422 may vary depending upon design criteria. In one implementation, the flex-stretch layer 422 has a hardness of about Shore 30D and is 1.2 mm thick. In some shoe constructions designed for running on track surfaces, the flex-stretch layer 422 is softer than Shore 30D. In other implementations, the flex-stretch layer 422 is harder than Shore 30D.

The rigid forefoot plate 408, and rigid toe plate 410 are made of a harder material than the flex-stretch layer 422. Suitable materials for one or more of the rigid plates include without limitation plastics, carbon-fiber, metal, rubber, synthetic rubber, Nylon (e.g., Nylon-12) and Pebax®. In various implementations, the hardness of the rigid plates ranges from Shore 40D to Shore 90D. The thickness of the rigid forefoot plate 408 and the rigid toe plate 410 may vary depending on material type and desired design criteria. However, in one implementation, the hardness of the plates is approximately Shore 70D. In another implementation, forefoot plate 408 and the toe plate 410 are about 1.5 mm thick.

The rigid toe plate 410 and the rigid forefoot plate 408 are separated from one another by a gap (e.g., in the y-direction, as shown in FIG. 4A) that spans a few millimeters (e.g., between about 3 mm and about 10 mm) or enough to allow for relative movement between the forefoot plate 408 and the toe plate 410 responsive to an applied force. The gap may of constant or variable thickness. In on implementation, the gap is 7 mm when measured on a medial (inside) of the sole construction 400 and 10 mm on a lateral (outside) edge of the sole construction 400.

The rigid forefoot plate 408 and the rigid toe plate 410 can be of a variety of different shapes and sizes. In one implementation, the forefoot plate 408 extends longitudinally toward the heel of the sole construction 400 and into a midfoot (i.e., arch) region and/or a heel region of the sole construction 400.

In FIG. 4, the forefoot plate 408 includes a flange portion 436 that extends from a forefoot region and into a midfoot region on a lateral side of the sole construction 400. One purpose of the flange portion 436 is to provide support for the bones in the fifth metatarsal of the user's foot. When running with proper form, the fifth metatarsal is the first part of the user's foot to contact the ground. Thus, injuries to the fifth metatarsal are common. The flange portion 436 of the rigid forefoot plate 402 may help to reduce the incidence of such injuries. In some implementations, the forefoot plate 408 does not include the flange portion 436.

A number of elongated slots (e.g., an elongated slot 414) are formed in the forefoot plate 408 and the toe plate 410, separating the forefoot plate 408 and the toe plate 410 into different, articulated regions. In various implementations, the number, length, and positioning of such slots may vary. In operation, the slots provide for independent movement of each of the articulated regions under force applied by associated regions a user's foot.

Track spikes (e.g., a track spike 434) are shown positioned in each of the rigid toe plate 410 and the rigid forefoot plate 408. In at least one implementation, these spikes can be selectively attached and/or detached by the user. For example, a track spike may include a grooved screw that twists and locks into a receiving slot. Functionally, the forefoot plate 408 and/or the toe plate 410 help to distribute a user's weight across evenly across the sole construction.

FIG. 5 illustrates an elevation view of another example shoe sole construction 500 during a mid-stance (e.g., contact) stage of a gait cycle. The shoe sole construction 500 includes a forefoot stretch flex zone 520 between a rigid forefoot plate 508 and a rigid toe plate 510. Material included in the stretch flex zone 520 between the rigid forefoot plate 508 and the rigid toe plate 510 is substantially more pliable than either of the rigid forefoot plate 508 or the rigid toe plate 510.

When in use, the rigid toe plate 510 underlies or substantially underlies a user's phalanges (i.e., toes), the rigid forefoot plate 508 underlies the user's metatarsal bones, and the stretch flex zone 520 substantially underlies the user's metatarsophalangeal joints. A midsole layer 518 receives and cradles the user's foot and separates the foot from the underlying rigid forefoot plate 508, rigid toe plate 510, and forefoot stretch flex zone 520. In at least one implementation, the midsole layer 518 is a softer (e.g., more pliable) material than the material of the stretch flex zone 520. Receiving divots (e.g., a receiving divot 516) may be formed on or attached to the toe plate 510 and/or the forefoot plate 508 to allow for attachment of one or more track spikes or other friction-providing elements.

A first axis “Y” indicates a torsional axis extending through toe and heel regions of the sole construction 500. A second axis “X” indicates a lateral axis extending through a forefoot region, between lateral and medial sides of the sole construction 500. When a runner's foot first strikes the ground, the runner's phalanges, metatarsals, and metatarsophalangeal joints may lie substantially flat within a common plane (e.g., within the X-Y plane as shown in FIG. 5). Then, as the runner pushes off of the ground during a “toe-off” phase of the gait cycle, the toes dorsiflex away from the rest of the foot, bending material of the shoe construction 500. An example flexure of the sole construction 500 responsive to dorsiflexion of the toes is shown in FIG. 6.

FIG. 6 illustrates another elevation view of a shoe sole construction 600 during a toe-off stage of a gait cycle. The shoe sole construction 600 includes a forefoot stretch flex zone 620 between a rigid forefoot plate 608 and a rigid toe plate 610. Material included in the stretch flex zone 620 between the rigid forefoot plate 608 and the rigid toe plate 610 is substantially more pliable than either of the rigid forefoot plate 608 or the rigid toe plate 610.

A first axis “Y” indicates a torsional axis that extends longitudinally through toe and heel regions of the sole construction 600. A second axis “X” indicates a lateral axis that extends through a forefoot region between lateral and medial sides of the sole construction 600. As a runner pushes off of the ground during a “toe-off” phase of the gait cycle, the toes dorsiflex away from the rest of the foot, bending material in the stretch flex zone 620 out of the x-y plane (e.g., in a z-direction).

In the same or another implementation, the stretch flex zone 620 is shaped to provide for additional rotation in another direction. For example, articulated regions in the forefoot plates (e.g., as shown in FIG. 2) may allow for torsional rotation of different regions of the sole construction 600 about Y or other axes substantially parallel to Y. In other implementations, the stretch flex zone 620 provides for rotational movement of the sole construction 600 about one or more axes non-parallel to the X or Y. For example, one or more articulated regions of the sole construction 600 may have freedom to move in more than two cardinal directions. In one implementation, the articulated regions in the forefoot plate 608 allow a user's metatarsals to strike the ground individually (e.g., one at a time) rather than all at once.

Receiving divots (e.g., a receiving divot 616) may be formed on or attached to the toe plate 610 and/or the forefoot plate 608 to allow for attachment of one or more track spikes or other friction-providing elements.

FIG. 7 illustrates example operations 700 for energy conservation in a sole construction. A providing operation 705 provides a sole construction with a flexible, stretchable material (i.e., a flex-stretch layer) in a forefoot region. The flex-stretch layer interconnects a first rigid plate to a second rigid plate across a gap between spanning a distance along a longitudinal axis of the sole construction. In one implementation, the flex-stretch layer is visible through the gap and forms a part of the ground-facing outer surface of the sole construction. In another implementation, one or more additional layers are formed between the flex-stretch layer and the ground-facing outer surface of the sole construction.

The first rigid plate is positioned so as to be vertically aligned or in contact with a portion of the flex-stretch layer extending into a toe region. The second rigid plate is positioned so as to be vertically aligned or in contact with another portion of the flex-stretch layer in the forefoot region. The first rigid plate and the second ridged plate may include a number of slots or gaps forming articulated regions.

In one implementation, the flex-stretch layer and the rigid plates are each positioned within a corresponding cut or depression in an overlying soft (e.g., foam) midsole layer. The flex-stretch layer is attached to the first rigid plate, second rigid plate, and the foam midsole layer through an adhesion process. In another implementation, the midsole layer is attached to the flex-stretch layer and the rigid plates via a co-injection process through which the elements are cohesively bonded through a molding process, or via a high-frequency welding process.

A force application operation 710 applies a contact force to a forefoot region of a sole construction. The force may be, for example, the weight of a runner applied to forefoot region of the sole when the runner's foot first strikes the ground. If the runner strikes the ground with a lateral edge of the foot so as to establish contact between the ground and the fifth (outermost metatarsal), the foot may have the tendency to rotate inward.

A torsional flex operation 715 flexes the flex-stretch layer in the region between the first rigid plate and the second rigid plate about a torsional axis, permitting two or more articulated regions of the first rigid plate and/or the second rigid plate to move independently of one another. In one implementation, a separate articulated region of the forefoot plate underlies each metatarsal of a user's foot. The user strikes the ground with one metatarsal at a time, from the outside in, until all five metatarsals are in contact with the ground.

A lateral flex operation 720 flexes the flex-stretch layer in the region between the first rigid plate and the second rigid plate about a lateral axis, permitting the first rigid plate to move relative to the second rigid plate. For example, the lateral flex operation may flex the sole construction about an axis below a user's metatarsophalangeal joints responsive to dorsiflexion of the user's toes. In other implementations, lateral and/or torsional rotation may occur in directions other than those described herein.

The above specification, examples, and drawings provide a complete description of the structure and use of exemplary implementations of the invention. Since many implementations of the invention can be made without departing from the spirit and scope of the invention, the invention resides in the claims hereinafter appended. Furthermore, structural features of the different implementations may be combined in yet another implementation without departing from the recited claims. 

1. A sole construction for a shoe comprising: a substantially flexible membrane in a forefoot region of the sole construction interconnecting a first substantially rigid plate to a second substantially rigid plate, the first substantially rigid plate axially aligned with the second substantially rigid plate along a longitudinal axis of the sole construction.
 2. The sole construction of claim 1, wherein the flexible membrane is adapted to flex in the forefoot region to allow movement of the first substantially rigid plate relative to the second substantially rigid plate.
 3. The sole construction of claim 1, wherein the first rigid plate is positioned in a toe region and the second rigid plate is positioned in the forefoot region.
 4. The sole construction of claim 1, wherein the first substantially rigid plate and the second substantially rigid plate are substantially planar and lie within a common plane in the absence of applied force.
 5. The sole construction of claim 1, wherein the flexible membrane forms part of a ground-facing outer surface of the sole construction.
 6. The sole construction of claim 1, wherein the second substantially rigid plate extends into a midfoot region on a lateral side of the sole construction.
 7. The sole construction of claim 1, wherein the first substantially rigid plate includes a number of articulated regions adapted to move relative to one another.
 8. The sole construction of claim 1, wherein the first substantially rigid plate includes five articulated regions adapted to move relative to one another.
 9. The sole construction of claim 1, further comprising a plurality of fastening means for attaching spikes to a ground-facing outer surface of the sole construction.
 10. The sole construction of claim 1, wherein the flexible membrane allows for movement of a portion of the first substantially rigid plate about both a torsional axis and a lateral axis, the torsional axis substantially perpendicular to the lateral axis.
 11. A method comprising: flexing a membrane in a forefoot region of a sole construction, the membrane connecting a first substantially rigid plate to a second substantially rigid plate, the first substantially rigid plate axially aligned with the second substantially rigid plate along a longitudinal axis of the sole construction.
 12. The method of claim 11, wherein the flexing operation moves the first substantially rigid plate relative to the second substantially rigid plate.
 13. The method of claim 11, wherein the first substantially rigid plate is positioned in a toe region and the second substantially rigid plate is positioned in the forefoot region.
 14. The method of claim 11, wherein the second substantially rigid plate extends into a midfoot region on a lateral side of the sole construction.
 15. The method of claim 11, wherein the first substantially rigid plate includes a number of articulated regions adapted to move relative to one another.
 16. The method of claim 11, wherein the first substantially rigid plate includes five articulated regions adapted to move relative to one another.
 17. The method of claim 11, wherein the membrane allows for movement of a portion of the first substantially rigid plate about both a torsional axis and a lateral axis, wherein the torsional axis is substantially perpendicular to the lateral axis.
 18. A sole construction comprising: a substantially rigid forefoot plate and a substantially rigid toe plate separated from one another and interconnected by a flexible membrane, the flexible membrane adapted to flex between the substantially rigid forefoot plate and the substantially rigid toe plate responsive to a contact force.
 19. The sole construction of claim 18, wherein the rigid forefoot plate includes a number of articulated regions adapted to move relative to one another.
 20. The sole construction of claim 19, wherein each articulated region is sized and shaped to underlie a corresponding metatarsal of a user's foot. 